Gyroscope with universally mounted rotor

ABSTRACT

A gyroscope with a universally mounted rotor including application as a north-seeking gyroscope. A planar, multiportion member transverse to a shaft axis and an axially rigid rod universally support the rotor on a rotating shaft. Magnetic trim means provide compensation to maximize decoupling of the rotor from the shaft.

United States Patent [1 1 Hildebrand July 31, 1973 1 GYROSCOPE WITHUNIVERSALLY MOUNTED ROTOR [75] Inventor: George L. Hildebrand,Marblehead,

Mass.

[73] Assignee: General Electric Company,

Wilmington, Mass.

[22] Filed: July 17, 1968 [21] Appl. No.: 745,494

[52] U.S. Cl. 1. 74/5 F [51] Int. Cl. G0lc 19/16 [58] Field of Search74/5 [56] References Cited UNITED STATES PATENTS 2,752,792 7/1956 Drapera a1 74/s.34 2,939,322 6/1960 Sedgfield et a1. 74/5 2,995,938

8/1961 Brodersen et a1 74/5.7

3,211,011 Litty 74/5 3,264,880 8/1966 Fischel 74/5 3,301,073 l/l967 Howe74/5.7 3,354,726 11/1967 Krupick et a1... 74/5 3,452,608 7/1969 Stiles74/5 3,489,016 1/1970 Quinby 74/5 Primary Examiner-Robert F. StahlAlt0rneyRichard E. l-losley, George A. Herbster, Frank L. Neuhauser,Oscar B. Waddell and Melvin M. Goldenberg [57] ABSTRACT A gyroscope witha universally mounted rotor including application as a north-seekinggyroscope. A planar, multiportion member transverse to a shaft axis andan axially rigid rod universally support the rotor on a rotating shaft.Magnetic trim means provide compensation to maximize decoupling of therotor from the shaft.

17 Claims, 7 Drawing Figures PATENTEBJUB 1 ms SHEET 1 OF 4 INVENTORGEORGE L HILDEBRAND PATENTEB JUL3 1 3. 748 912 SHEET 2 [IF 4 INVENTORGEORGE L, HILDEBRAND ATTORNEY PATENIED 3.748.912

sum 3 OF 4 INVENTOR GEORGE L. HILDEBRAND A TORNEY PATENTED I I975 3.748.912

SHEET k (If 4 H06 my h u CONTROL cmcun UTILIZATION i cmcun I26 I34 1 II4I ICIIII CONTROL F CIRCUIT Y AXIS PICKOFF CONTROL cmcun INVENTORUTILIZATION CIRCUIT GEORGE L. HILDEBRAND ATTORNEY GYROSCOIE WITHUNIVERSALLY MOUNTED ROTOR BACKGROUND OF THE INVENTION This invention isdirected to gyroscopes and more particularly to gyroscopes in which arotor is universally mounted to a driving shaft.

This application of a universal joint structure to mount a rotor to ashaft in a gyroscope has a wide range of applications. For example, rategyroscopes including such universally mounted rotors can sense relativedisplacement of a supporting structure and the rotor to thereby indicatethe magnitude and direction of a rate vector. Specifically, a rate gyrocould constitute a north-seeking gyroscope with the rate gyro assemblysensing the earths rate vector in a horizontal plane. In aircraft,prefiight alignment of a low drift rate gyroscope system to true northcould furnish sufficiently accurate navigational information in flight,such as azimuth information, especially where magnetic charts were notavailable or were inaccurate. In another application surveying equipmentcould be oriented with a rate gyroscope to provide alignment at a remotelocation.

In another broad application, a gyroscope with a universally mountedrotor could constitute a two-axis inertial reference to stabilizenavigational platforms. A universally connected rotor, decoupled fromthe shaft, is a free rotating body in space; and the platform could bestabilized by follow-up control systems which realign the platform withthe decoupled rotor.

The application of universal joints to gyroscopes has been attempted fora number of years, and the universal joints have taken several diverseforms. In one of the earliest approaches, a universal joint includingtwo sets of bearing members joined on perpendicular axes connected arotor to a driving shaft. Later, a ball and socket arrangement providedthe universal connection. In another approach, the rotor shaftconnecting the driving portion to the rotor was necked down to produce aflexure. Yet another approach incorporated cross flexure members incombination with gimbal like rings. Still another universal jointassembly has utilized paralled, integral, universal joints tointerconnect the rotor and the driving shaft.

Each approach has recognized specific operating problems which arise inthe construction of any gyroscope incorporating a universally connectedrotor. Basically these problems stem from the friction or springconstants of the universal joints which produce precessional torques andunacceptable drift rates. Further, certain approaches aimed atovercoming the drift problem have required an extremely complexconstruction for both the universal joint and the gyroscope. In otherapproaches the rotor must be operated at a critical speed to completelydecouple the rotor thereby requiring special driving means calibratedfor each individual gyroscope.

Alternatively means to vary the universal joint dynamic configurationhave been provided. When positivespring forces were assured, magnetsattracted the rotor when it was displaced from the shaft axis to act asa negative spring and cancel torques exerted by deflection of theuniversal joint. Mechanically adjustable internal members associatedwith the universal joint to vary the inertia and compensate for speedvariations have also been incorporated. Neither approach permittedsimple compensation or calibration after the completed system wasconstructed so interchangeability of the gyroscope with different powersupplies required complex balancing techniques before completedecoupling was assured.

Therefore, it is an object of this invention to provide an improvedconstruction for a universal joint which minimizes gyroscope drifterrors.

Yet another object of this invention is to provide a universal jointadapted for mounting in a gyroscope without adverse affecting theoverall gyroscope size.

Still yet another object of this invention is to provide a gyroscopeincluding means for adjusting and balancing a universally mounted rotorexternally from the gyroscope.

Another object of this invention is to provide a gyroscope which isespecially adapted for platform stabilization.

Yet still another object of this invention is to provide a gyroscopewhich is especially adapted for use in determining the location of truenorth.

SUMMARY In accordance with one aspect of this invention, a rotor isuniversally connected to a driving shaft by a planar, multiportion,integral member. Certain portions, affixed to the rotor and shaft, areuniversally connected together. Means are provided to minimize axialdisplacement of the rotor relative to the shaft. Other means react withthe rotor and produce countertorques to minimize drift.

This invention is pointed out in the appended claims. The above andfurther objects and advantages of this invention may be betterunderstood by referring to the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically illustrates agyroscope assembly mounted in a Cardan suspension;

FIG. 2 is a section of a gyroscope constructed in accordance with thisinvention;

FIG. 3 is a diagram useful in understanding the theory of thisinvention;

FIG. 4 is a detailed view of one portion of a universal joint assemblyshown in FIG. 2;

FIG. 5 illustrates a pickoff and torquer arrangement in a gyroscope andis taken along lines 5-5 in FIG. 2;

FIG. 6 illustrates a system utilizing a universally mounted rotor on agyroscope for stabilizing a platform in space; and

FIG. 7 illustrates a system utilizing a universally mounted rotor on agyroscope in a system for determining true north.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS Although this invention may beutilized in various reference system configurations, one exemplaryconfiguration is outlined in FIG. I. A gyroscope 10 which contains arotating inertial mass therein is suspended to rotate about a minor axisdefined by trunnions ll affixed to a gimbal 12, the gimbal 12 beingrotatable about a major axis defined by trunnions 13 supported on afixed support member generally designated by 14. Hence, the entireassembly provides 2 of freedom for the gyroscope in a conventionalCardan suspension. In-

dications of the relative positions of the gyroscope 10.,

the gimbal 12 and the support member 14 may be obtained by means ofpickoffs 15 and 16. The outputs of these pickoffs may be coupled to autilization circuit 17 including means for displaying the relativepositions of the gimbals or means for performing a control function.

To control rotation about the minor axis, a torquer 20 is locatedtodrive the trunnions 13 by applying a torque about the major axis. Sucha torque acts, through the gyroscope precession, to rotate the gyroscope10 about the minor axis. Similarly, another torquer 21 associated withthe trunnions 11 applies torque about the minor axis to rotate thegimbal 12 about the major axis. Both torquers 20 and 21 may be energizedby a power supply 22 which may be under control of the pickoff signalsas is known in the art.

The exact construction of the gyroscope 10 is not critical to anunderstanding of this invention. For purposes of this discussion,however, a symmetrical gyroscope such as that described and claimed inUS. Pat. No. 2,731,836, issued to Harry C. Wendt on Jan. 24, 1956, andassigned to the same assignee as the present invention is specificallyshown in FIG. 2. A planar frame member 23 supports a shaft 24 at rightangles thereto. Mounted on one side of the frame member 23 are statorwindings 25. Hysteresis material 26 is affixed on a lower rotor 27connected for rotation with the shaft 24 which is mounted in the planarmember 23 by bearings 30 captured in the frame member 23. Energizationof the stator windings causes the shaft 24 to be rotated at a speeddependent upon the frequency of theapplied power. Means for connectingthe stator windings to the power supply are well known in the art andare omitted for purposes of clarity. The lower rotor 27 may have aninertia which is of the same order of magnitude as an upper rotor 31.This upper rotor includes internal pickoff assemblies 32 and torquers 33which react with magnetically conducting portions 34 onthe upper rotor31. In accordance with this invention, the upper rotor 31 is connectedto the shaft 24 by a universal joint assembly 35 so that the upper rotor31 may be decoupled from the shaft 24.

It will be useful to consider FIG. 3 and the theory of a universal jointgyro, particularly of the specific universal assembly describedhereinafter. A driving member 36 rotates a shaft 37 about a Z axis withX and Y axes perpendicular to each other and mutually perpendicular tothe Z axis. Connected to the shaft 37 and to a rotor 40 is a universaljoint 41. Although the universal joint 41 is an integral member, it isspaced along the Z axis for purposes of clarity in FIG. 3. A firstportion 42 of the universal joint 41 is connected to the shaft 37. Asecond portion 43 is connected to the rotor 40. The first and secondportions 42 and 43 are then connected to an intermediate portion 44 bymeans of connecting portions 45 and 46. Each connecting portion istorsionally compliant along axes defined thereby so the intermediateportion 44 can rotate with reference to the first portion 42 and thesecond portion 43. Hence, the rotor 40 can be displaced from the Z axisto rotate about other axes. During such displacement, the intermediateportion 44 defines, at a given instant in time, three axes, a, b and c,displaced from the X, Y and Z axes. It is assumed that no forces actalong the Z axis which tend to displace the rotor 40 in the followingtheoretical discussion and that displacement of the rotor 40 is limitedto small angles.

The average torques developed about the X, Y and Z axes for a deflectionof the rotor 40 about the Y axis during a complete revolution are:

ztv) o tan (Bu tan (Bu sinz (Bu Sin (Bu) 0) [By/ (311)] tan (Bu [K cos(B K cos (B /2)] and T T 2mn sec (3,) sin (B /2) qn [sec (B,,) COS(BUT-( hr) a a) Bu CO8 (1 u b) tanz (Bu) K0 (Bi/) l However, T T,,,, thewindage torque, and B the angle of deflection, is small so sin ([3,) tan(5,) ,6, and cos (8,) sec (B 1. By manipulating the equations, solvingequation (3) for T, and substituting it in equation (1), equations (1)and (2) are reduceable to:

and

where:

F, dry friction along a axis F dry friction along b axis n speed of thedrive shaft K, viscous friction coefficient along 4 axis K viscousfriction coefficient along b axis a intermediate portion inertia about aaxis b intermediate portion inertia about b axis 0 intermediate portioninertia about 0 axis In an integral universal joint where only torsionalforces are developed within the universal joint,

F, F O

and

T1111) Tw Bu Deflection of the rotor 40 about the Y axis also causes aspring force to be developed by the universal joint which appears as atorque component KB about the Y axis where K is the spring constant. Soequation (5) becomes:

A similar analysis for deflection of the rotor 40 about the X axis showsthat:

and

IM-I) 1b an .1:

By combining equations (8) and (10) and equations (9) and (I 1), thetotal torque for any deflection of the rotor can be defined as:

If it is assumed that T is negligible in comparison with the other termsin the equations, then when and the rotor 40 is effectively decoupledfrom the shaft 37.

As shown in FIG. 2, the upper rotor 31 is connected to an upper shaftportion 47 by means of a planar member 50 and an axially rigid rod 51.These two members, which include an inertia member 52 with polar andtransverse moments of inertia constitute a universal joint connected tothe upper shaft portion 47 by a collar assembly 53 and to the upperrotor 31 in accordance with the theory and assumptions discussed inreference to FIG. 3.

FIG. 4 illustrates the details of the planar member 50 having agenerally circular outline. Specifically, an outer portion 54 with aplurality of apertures 55 formed therethrough is connected to the upperrotor 31 by means of an insert assembly 56 and a plurality of bolts 57which extend through the apertures 55 as illustrated in FIG. 2. Hence,the outer portion 54 shown in FIG. 4 is retained in a planarorientation, the plane being defined by the position of the upper rotor31 with respect to the shaft.

Two identical portions 60 with a plurality of apertures 61 are disposedat the opposite ends of an elongated opening 62 formed in the-planarmember 50 and essentially bounded by the outer portion 54. Each portion60 is connected to the collar assembly 53 shown in FIG. 2 by clampingthe identical portions 60 thereto with a clamp 63. These elementsarepositioned by a bolt 64 or other securing means.

As specifically shown in FIG. 2, the collar assembly 53 has a taperedinner surface 65 which is forced over a complementary tapered surface onthe upper shaft portion 47. Hence, the identical portions 60 aremaintained in a constant planar orientation. This plane is defined bythe collar assembly 53 and is always transverse to the axis of rotationof the shaft 24.

Referring again to FIG. 4, the first portion 54 and the identicalportions 60 are universally connected by an intermediate portion 70. Theintermediate portion hasmeans, such as a plurality of apertures 71,formed therethrough for connecting the inertia member 52 thereto toconstitute a conventional universal joint spider. In addition, theintermediate portion 70 and inertia member 52 have a central aperture 72to permit the upper shaft portion 47 to pass therethrough. Thisintermediate portion 70 is connected by torsionally compliant strips 73and 74 to the outer portion 54 and by torsionally compliant strips 75and 76 to the identical portions 60 so the intermediate portion 70 iscapable of rotation relative to the upper rotor 31 about an axis throughthe strips 73 and 74 and relative to the collar assembly 53 about anaxis defined by the strips 75 and 76. Hence, the upper rotor 31 isuniversally connected to the upper shaft portion 47.

As the intermediate portion 70 has the inertia member 52 rigidly affixedthereto, a polar moment exists for the assembly which is equivalent tothe spider polar moment described above. If the rotor speed ismaintained in accordance with equation (14), the torques about the X andY axes relative to the drive shaft are zero. Thermal stability can beobtained by forming the universal joint of Ni-Span C or other materialwhich has a thermally stable elastic modulus.

Lateral and torsional stability for the upper rotor 31 exist with thisconstruction of the planar member 50. However, the planar member 50shown in FIG. 2 i s'not axially stable with respect to the shaft 47.Means must be provided to achieve axial stability. One such means is anaxially rigid rod 51 which is affixed to the upper rotor 31 and to theupper shaft portion 47. One end of the rod 51 is permanently affixed ina bushing 77 which is coaxial with the rod. The bushing 77 engages therod along a portion 78, but is spaced from the rod 51 along theremaining bushing length. It is disposed in an axial bore 80 formed inthe upper shaft portion 47 to be internally spaced from the end of thebore 80 to permit compensation of differential thermal coefficients ofexpansion. Axial movement of the bushing 77 is prevented by engagementof a conical surface 81 formed at the end of the upper shaft portion 47and a complementary conical surface 82 formed on the bushing 77. A nutassembly 66 with a conical surface 83 formed thereon bears on anotherouter conical surface 84 formed on the bushing 77 when the nut 66 istightened on the threaded portion 67 of the upper shaft portion 47.

The other end portion 85 of the rod 51 is permanently affixed to aninsert 86 which is clamped to the upper rotor 31. The end portion 84 iscoaxial with the axis of rotation of the upper rotor 31.

When assembled, the bushing 77 orients the rod 51 so that the endportion 78 is coaxial with the axis of rotation of the shaft 24. Theinsert 86 orients the end portion 85 of the rod 51 so that it is coaxialwith the axis of rotation for the upper rotor 31. For small deflectionsof the rotor axis from the shaft axis, the rod 51 maintains its axialrigidity to thereby provide the universal joint with the property ofbeing free from axial forces. However, the rod is compliant about axestransverse to the shaft axis.

Therefore, as the universal joint assembly in FIG. 2 is axially stable,the theoretical assumptions may be practicably satisfied. Further, therequirements of equation 14 can be met so that no appreciable drift willresult from internal forces or torques generated by the universal jointduring rotor displacement. Relative ease of repeatable universal jointmanufacture may be realized because the planar member 50 is thin and canbe formed by means other than punching or machining. In someapplications conventional photo-etching techniques may be used. Thesetechniques are highly accurate so manufacture of a planar member withrepeatable characteristics is simplified.

Portions of a pickoff assembly 32 and a torquer 33 which sense andcontrol the position of the upper rotor 31 are shown in FIG. '2. Theorientation of a pickoff and torquer system may be understood byreferring to FIGS. 2 and simultaneously. In this particular embodiment,the torquer 33 comprises a coil 90 disposed on an axially extendingannular frame member 91 which is integrally formed with the frame member23. Affixing the torquer coil 90 to the supporting member 91 will bedescribed more fully hereinafter. An annular, radially poled magnet 92is located in the upper rotor 31 and lies in a plane transverse to theupper rotor axis of rotation. Annular pole shoes 93 and 94 areconcentrically mounted to the upper rotor 31 and depend from the radialterminations of the magnet 92 to be partially axially coextensive withthe torquer coil 90. Therefore, the coil 90 and the magnet assembly inthe upper rotor 31 together constitute a dArsonval torquer arrangement.

Four torquer windings are equiangularly spaced about the support member91 in this particular embodiment. In addition to the torquer 33,torquers 95, 96 and 97 are shown in FIG. 5 so that the torquers 33 and96 lie on one axis while the torquers 95 and 97 lie on an axisperpendicular thereto. It will be obvious to those skilled in the artthat additional torquers can be disposed about the periphery of thesupport member if further torquing resolution is desired. Alternativelyfewer torquers might also be utilized in particular applications.-

FIG. 2 shows one portion of a pickoff assembly 32 which is alsosupported on a frame 23. The pickoff assembly specifically shown in theembodiment of FIGS. 2 and 5 utilizes the principal of an E pickoff inwhich the sensing portions are designated by numerals 99, 100, 101 and102. lntermediately located between the sensing units are theenergization units 103, 104, 105 and 106. As all the picltoffsensing'units are identically constructed and as all the energizingunits are identically constructed, a detailed discussion of these unitsis limited to the pickoff sensing unit 99 and the energizing unit 103.As specifically shown in FIG. 2, the pickoff sensing unit 99 includes acoil 107 which is wrapped about a pole piece 110 with a pole face 1R1being formed coextensively with the surface at the depending pole shoe94 on the upper rotor 31. The surface of the outer pole shoe 94 and thepole face 111 are radially formed about the center of gravity of theupper rotor 31. The energizing member 103 includes two radiallyextending poles. An upper pole 112 and a lower pole 1 13 have coils 1 14and 115 wrapped thereupon. The coils 114 and 115 are wound so theyproduce fluxes which are in the same direction in a loop magneticcircuit. The pole surfaces 116 of the energizing member 103 are alsoarcuately formed about the center of gravity of the upper rotor 31.

Assume that forces act on the gyroscope to move the frame 23 and thepicltoff sensing unit 99, relative to the upper rotor 31 to cause aportion of the pole shoe 94 adjacent to energizing coil 103 to movetoward the upper pole 1 12. The reluctance between the upper pole 112and the pole shoe 94 is decreased while the reluctance between the poleshoe 94 and the lower pole 113 is increased. As the poles associatedwith all the energizing members and pickoff members are magneticallyconnected by a ring portion 117, a component of flux produced in theupper pole H2 is not carried by the lower pole 113. Instead it travelsthrough the pole shoe 94 to the piclroffs and 101. Similarly, flux willtravel from the energizing unit 104 and to the pickoffs 101 and 102.However, at the energizing units and 106 the lower pole-to-pole shoereluctance will be decreased and the component of magnetic flux from thelower pole not coupled to the upper pole passes through the pole shoe 94to the adjacent pickoff sensing units. As all the coils on the upperpoles and all the coils on the lower poles arewound to be of the samepolarity, the net flux through the pickoffs 102 and 100 will be zero.However, the flux components in the energizing units 106 and 105 will becoupled to the pole and coil 107 of the pickoff'sensing unit 99 in thesame direction to produce an AC voltage of a given phase. At the pickoffsensing unit 101 the flux will be of the opposite polarity so an ACvoltage 180 out of phase with the voltage produced at the pickoffsensing unit 99 will be produced. A similar analysis will show thatother movements of the upper rotor 31, different voltages will beproduced at the various pickoffs and these will indicate the directionand magnitude of the input force vector applied to the gyroscope.

When the rotor axis and the shaft axis are aligned, the pole shoe 94 isso disposed so the reluctance between the upper pole and the pole shoeand the lower pole and the pole shoe for each energizing unit areidentical. Therefore, all the flux in the poles is coupled through thepole shoe 94 and back to the energizing unit so no flux links any of thepickoff coils.

A power supply for a given gyroscope using a universal joint can beconstructed to provide a rotational speed in accordance with equation14. However, in repetitive manufacture it is extremely difficult tomaintain tolerances whereby substantially no inertia variations occur sothat a given rotor speed would produce complete decoupling for allgyroscopes. Minor variations in the frequency can also occur to vary thespeed of the gyroscope rotor. in addition a windage torque may exist tothereby add an additional torque to the system. As another aspect ofthis invention, therefore, compensation schemes are provided to assurecomplete decoupling of the rotor.

In accordance with equations (12) and (13) torques are produced aboutthe X and Y axes only when the rotor and shaft axes of rotation are notcoincidental. When the power supply and rotor are not properly mated,the rotor speed may vary from that of equation (14). Therefore tomaintain complete decoupling a counte'rtorque must be applied which is:

counter torque bi /2 (a-l-b-c) K} 5,.

To this end a coil 120' is mounted to the support 91 so that half thecoil 120 lies parallel to and coextensively with the inner annular poleshoe 93. This coil 91 is adapted to be energized by a direct currentwhich is variable in magnitude and polarity. In the particularembodiment shown, the coil 91 and the torquer coils 90 are bondedtogether and to the vertical support 91. As an alternative, the coilcould be substituted by a single turn of foil, half of the turn beingcoextensive with the inner pole shoe 93. In either approach,energization of the coil 120 produces a uniform flux density withrespect to the axis of the coil 120.

Once a gyroscope system is completed, and assembled, the only variablein equation (16) is [3,. Assume that the frame 23 in FIG. 2 moves withrespect to the X axis. This produces a torque which tends to cause thegyroscope to precess about the Y axis. However, the movement of therotor about the X axis unbalances the forces applied by the coil 120 tothe upper rotor 31. By choosing the polarity and magnitude of currentenergizing the coil 120 properly, a counter torque is applied to theupper rotor 31 which cancels the torque produced by the speed variation.I

Small windage torques may also exist which could cause drift. Thewindage is minimized by encasing the entire gyroscope. However, driftcaused by such wind age torques should be a function which isproportional to the rotor displacement so the torquers 33, 95, 96 and917 can be energized by a controlled current to provide compensation.Therefore, if conditions of the assumptions are not obtainable, meansfor compensating resultant drift-can be and are provided.

A gyroscope which utilizes a universally connected rotor can be used ina number of configurations. While many modifications and alternativeconstructions can be evolved for a number of uses, FIGS. 6 and 7 presenttwo applications and embodiments of a gyroscope system configuration asshown in FIG. 1. For example, a system for stabilizing a platform 121 inspace is schematically shown in FIG. 6. A rotor 122 is universallymounted to the platform 121 and pickoffs 123 and 124 sense the positionof the rotor 122 with respect to the platform 121. Assuming that therotor 122 is completely decoupled from the platform 121 while rotating,any deviation of the platform 121 and the spin axis of the shaft will besensed by the pickoffs 123 and 124, thereby producing signals fed to acontrol circuit 125.

Signals from the control circuit may then be applied to externaltorquing means. For example, the platform 121 might be connected throughtrunnions 126 to a gimbal 127 while the gimbal 127 would be coupled to asupporting frame 130 by trunnions 131. Torques could be applied througha torquer 132 and a torquer 133 with thepositions of the gimbal 127 andthe platform 121 being sensed by pickoffs 134 and 135. With thisfollow-up system any movement of the platform 121 with respect to therotor 122 would be sensed in the pickoffs 123 and 124. Torques would beapplied through the torquers 132 and 133 to realign the platform 121 tothe rotor 122. As the rotor 122 is completely decoupled from theremainder of the gyroscopic assembly, the platform 121 would thereby bestabilized in space.

Another schematic is shown in FIG. 7 in which a rotor 140 is universallymounted to a shaft. X and Y axes pickoffs 141 and 142, equivalent to thepickoffs larly, the energization of an X axis torquer is varied by acontrol circuit 146 responsive to the Y axis pickoff 122. A resolvercircuit including windings 147, an amplifier and a servomotor 151 areconnected to the control circuits 143 and 146. The motor output iscoupled by a shaft 152 to a utilization device 153.

If the drive shaft for the rotor 140 is vertically oriented and thegyroscope is fixed, the gyro rotor drive shaft tends to be deflected bythe horizontal component of the earths rotation with respect to therotor 140. The pickoffs 141 and 142 sense any deflection caused by thisrate vector and act through the control circuits 143 and 146 to applytorques and rebalance the rotor 140. The currents required for therebalancing are then monitored in the resolver windings 147. When theamplifier 150 and servometer 151 act as a rebalancing network, thedirection of the horizontal component of the earths rate is indicated.As this horizontal rate vector lies on a north-south line, true northmay be easily indicated. A true north indication may thereby be readilyobtained in a variety of vehicles or applications merely by energizingthe gyroscope, and its associated circuitry, stabilizing the shaft inthe vertical direction and force-balancing the rotor 31.

It will be obvious to those of ordinary skill in the art that thephysical embodiment of the invention described above may take manyforms. Different gyroscope arrangements, different torquer arrangements,different pickoff arrangements, various other means forelectromagnetically compensating for changes in speed, and othervariations may be made without departing from the true spirit and scopeof the invention. Therefore, it is the object of the appended claims tocover all such modifications which come within the true spirit and scopeof the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a gyroscope including a shaft, means for driving the shaft about ashaft axis and a rotor to be rotated about a spin axis, a mountingassembly universally connecting the rotor to the shaft comprising:

a. An integral substantially planar member having universally coupledportions connected to the rotor and shaft comprising first and secondportions connected to the rotor and shaft, respectively, a substantiallyrectangular intermediate inertial portion having an inertia memberconnected thereto for increasing the polar and transverse moment of saiduniversal mounting, and first and second pairs of connecting portionsfor said intermediate portion said second portion being connected tosaid intermediate portion to be substantially adjacent opposite sides ofsaid intermediate portion and said intermediate and second portions liein an elongated opening substantially peripherally surrounding saidintermediate and second portions, said first portion being connected tosaid intermediate portion by connecting portions between said firstportion and the other side of said intermediate portion,

b. an axially rigid, bendable member connected to the rotor and shaft,portions of said member remaining coaxial with the shaft and spin axes.

2. A gyroscope as recited in claim 1 wherein said planar member and saidaxially stiff member are formed of a material which exhibitssubstantially no spring constant variation over a thermal operatingrange.

3. A gyroscope comprising:

a. a support means;

b. a rotor;

c. a driven shaft mounted to said support means for rotation about ashaft axis;

(1. a substantially planar member comprising a first portion connectedto said rotor, a second portion connected to said shaft, and an inertialportion connecting said first and second portions along first and secondperpendicular axes, said rotor thereby being connected to said drivenshaft to be rotated about a rotor spin axis;

. an axially stiff rod having a first portion coaxially connected tosaid shaft and a second portion connected to said rotor coaxially withsaid gyro spin axis, said rotor thereby being universally connected tosaid shaft;

f. means for rotating said driven shaft at a speed substantiallycanceling torques produced by said planar member and said axially stiffrod; and

g. means on said support means and said rotor operating to sense andindicate relative displacement of said rotor and support means.

4. A gyroscope as recited in claim 3 wherein said planar member includesinertia means integrally mounted thereon, the rotor speed beingmaintained so that a substantially zero net torque acts on said rotorand trim means connected to said rotor and said support meansinteracting to substantially eliminate the development of such torquesby rotor speed variations during rotor displacement.

5. A gyroscope as recited in claim 3, said first portion of said planarmember being a substantially cylindrical member, said inertial portioncomprising a substantially rectangular member located centrally in anelongated aperture formed in said first portion, said second portionlying on either side of said intermediate portion in said elongatedaperture, said first portion being connected to said second portion by afirst pair of connecting portions and said second'portion beingconnected to said intermediate portion by a second set of connect ingportions perpendicular to said first connecting portions, saidconnecting portions being integrally formed with said planar member tobe compliant about the perpendicular axes and laterally and torsionallystiff with respectto. the shaft axis.

- 6. A gyroscope as recited in claim 5 wherein said trim means comprisesan electrical solenoid having a coil mounted on said support means andan armature mounted on said rotor, energization of said solenoid causingcomplete decoupling of said rotor from said shaft.

7. A gyroscope as recited in claim 6 whereinsaid electrical solenoid isconstituted by anelectrical coil concentric with said shaft, an annularmagnet disposed in said rotor and pole shoes connected to said magnet,said pole shoes being partially axially coextensive with said coil whenthe rotor spin and drive shaft axes are aligned.

8.'A gyroscope as recited in claim 6 wherein said coil is mounted onsaid stator and is adapted to be energized by a reversible directcurrent, said magnet and pole shoes being mounted on said rotor, saidpole shoes additionally serving to coact with said displacement sensingmeans.

9. A gyroscope as recited in claim 6 additionally comprising means forstabilizing and orienting said gyroscope with a vertical shaft axis andforce balancesaid rotor is decoupled from the shaft to indicate angularvelocity of the gyroscope in a horizontal plane.

10. A gyroscope as recited in claim 9 wherein said force balance meanscomprises a plurality of torquer and electrical pickoff means responsiveto and acting upon said rotor to force balance said rotor, saidgyroscope additionally including resolving means energized in responseto said pickoff and torquer signals to indicate the orientation of saidgyroscope with respect to said rotor.

11. In a gyroscope including a drive shaft and means for rotating thedrive shaft, a rotor and universal joint means having a spring constantand an inertia for connecting the rotor to the drive shaft, the drivingmeans rotating the drive shaft at a speed which substantially cancelstorques introduced by displacement of the rotor, the improvement ofmeans for cancelling the displacement torques comprising solenoid meansincluding the rotor mounted for exerting a torque on the rotorproportional to the rotor displacement.

12. A gyroscope as recited in claim 11 wherein said solenoid means isconstituted by coil means mounted on said stator and an annular,radially polarized magnet adapted for mounting on the rotor.

13. A gyroscope as recited in claim 12 wherein said coil isconcentrically mounted and is adapted to be energized by a reversibledirect current and a pair of radially spaced, annular pole shoes axiallyextending from said magnet to be partially axially coextensive with saidcoil whereby a torque is exerted on the rotor during rotor displacement.

14. A gyroscope as recited in claim 13 wherein the universal joint isconstituted by a planar member generally transverse to said shaft axishaving portions connected to the rotor and stator which are universallyconnected through an intermediate portion having a moment of inertia andmeans'for preventing axial displacement of the rotor and the shaft.

15. A north-seeking gyroscope including a gyroscope having a universallymounted rotor decoupled from a vertically oriented driving shaft,pickoff and torquer means formed on the gyroscope and interconnected totorque-balance the rotor when the shaft is moved in response to theearths rotation and means energized by said pickoffs and torquers forresolving signals therefrom into an indication of the position of truenorth.

16. A north-seeking gyroscope as recited in claim 15 wherein said rotoris connected to said drive shaft by a transverse planar member havingportions connected to the rotor and the shaft which are universallyconnected through an intermediate, inertia portion on two perpendicularaxes and means for preventing axial movement of the rotor with respectto the shaft, said gyroscope additionally comprising means for drivingthe rotor at a speed at which the inertia and spring constants of theuniversal joint are canceled.

17. A gyroscope as recited in claim 16 additionally comprising solenoidmeans including an axially extending coil concentrically disposed withrespect to the shaft axis adapted to be energized by a direct currentsource, an annular, radially polarized magnet, and a pair of radiallyspaced, annular pole shoes axially extending from the radialterminations of said magnets to be partially axially coextensive withsaid coil when the rotor spin axis and the shaft axis are alignedwhereby energization of the coil produces a torque about the gyroscopeaxes which compensates for torques produced when said rotor isdisplaced.

' i l 8 I i

1. In a gyroscope including a shaft, means for driving the shaft about ashaft axis and a rotor to be rotated about a spin axis, a mountingassembly universally connecting the rotor to the shaft comprising: a. Anintegral substantially planar member having universally coupled portionsconnected to the rotor and shaft comprising first and second portionsconnected to the rotor and shaft, respectively, a substantiallyrectangular intermediate inertial portion having an inertia memberconnected thereto for increasing the polar and transverse moment of saiduniversal mounting, and first and second pairs of connecting portionsfor said intermediate portion said second portion being connected tosaid intermediate portion to be substantially adjacent opposite sides ofsaid intermediate portion and said intermediate and second portions liein an elongated opening substantially peripherally surrounding saidintermediate and second portions, said first portion being connected tosaid intermediate portion by connecting portions between said firstportion and the other side of said intermediate portion, b. an axiallyrigid, bendable member connected to the rotor and shaft, portions ofsaid member remaining coaxial with the shaft and spin axes.
 2. Agyroscope as recited in claim 1 wherein said planar member and saidaxially stiff member are formed of a material which exhibitssubstantially no spring constant variation over a thermal operatingrange.
 3. A gyroscope comprising: a. a support means; b. a rotor; c. adriven shaft mounted to said support means for rotation about a shaftaxis; d. a substantially planar member comprising a first portionconnected to said rotor, a second portion connected to said shaft, andan inertial portion connecting said first and second portions alongfirst and second perpendicular axes, said rotor thereby being connectedto said driven shaft to be rotated about a rotor spin axis; e. anaxially stiff rod having a first portion coaxially connected to saidshaft and a second portion connected to said rotor coaxially with saidgyro spin axis, said rotor thereby being universally connected to saidshaft; f. means for rotating said driven shaft at a speed substantiallycanceling torques produced by said planar member and said axially stiffrod; and g. means on said support means and said rotor operating tosense and indicate relative displacement of said rotor and supportmeans.
 4. A gyroscope as recited in claim 3 wherein said planar memberincludes inertia means integrally mounted thereon, the rotor speed beingmaintained so that a substantially zero net torque acts on said rotorand trim means connected to said rotor and said support meansinteracting to substantially eliminate the development of such torquesby rotor speed variations during rotor displacement.
 5. A gyroscope asrecited in claim 3, said first portion of said planar memBer being asubstantially cylindrical member, said inertial portion comprising asubstantially rectangular member located centrally in an elongatedaperture formed in said first portion, said second portion lying oneither side of said intermediate portion in said elongated aperture,said first portion being connected to said second portion by a firstpair of connecting portions and said second portion being connected tosaid intermediate portion by a second set of connecting portionsperpendicular to said first connecting portions, said connectingportions being integrally formed with said planar member to be compliantabout the perpendicular axes and laterally and torsionally stiff withrespect to the shaft axis.
 6. A gyroscope as recited in claim 5 whereinsaid trim means comprises an electrical solenoid having a coil mountedon said support means and an armature mounted on said rotor,energization of said solenoid causing complete decoupling of said rotorfrom said shaft.
 7. A gyroscope as recited in claim 6 wherein saidelectrical solenoid is constituted by an electrical coil concentric withsaid shaft, an annular magnet disposed in said rotor and pole shoesconnected to said magnet, said pole shoes being partially axiallycoextensive with said coil when the rotor spin and drive shaft axes arealigned.
 8. A gyroscope as recited in claim 6 wherein said coil ismounted on said stator and is adapted to be energized by a reversibledirect current, said magnet and pole shoes being mounted on said rotor,said pole shoes additionally serving to coact with said displacementsensing means.
 9. A gyroscope as recited in claim 6 additionallycomprising means for stabilizing and orienting said gyroscope with avertical shaft axis and force balance means responsive to displacementof said rotor when said rotor is decoupled from the shaft to indicateangular velocity of the gyroscope in a horizontal plane.
 10. A gyroscopeas recited in claim 9 wherein said force balance means comprises aplurality of torquer and electrical pickoff means responsive to andacting upon said rotor to force balance said rotor, said gyroscopeadditionally including resolving means energized in response to saidpickoff and torquer signals to indicate the orientation of saidgyroscope with respect to said rotor.
 11. In a gyroscope including adrive shaft and means for rotating the drive shaft, a rotor anduniversal joint means having a spring constant and an inertia forconnecting the rotor to the drive shaft, the driving means rotating thedrive shaft at a speed which substantially cancels torques introduced bydisplacement of the rotor, the improvement of means for cancelling thedisplacement torques comprising solenoid means including the rotormounted for exerting a torque on the rotor proportional to the rotordisplacement.
 12. A gyroscope as recited in claim 11 wherein saidsolenoid means is constituted by coil means mounted on said stator andan annular, radially polarized magnet adapted for mounting on the rotor.13. A gyroscope as recited in claim 12 wherein said coil isconcentrically mounted and is adapted to be energized by a reversibledirect current and a pair of radially spaced, annular pole shoes axiallyextending from said magnet to be partially axially coextensive with saidcoil whereby a torque is exerted on the rotor during rotor displacement.14. A gyroscope as recited in claim 13 wherein the universal joint isconstituted by a planar member generally transverse to said shaft axishaving portions connected to the rotor and stator which are universallyconnected through an intermediate portion having a moment of inertia andmeans for preventing axial displacement of the rotor and the shaft. 15.A north-seeking gyroscope including a gyroscope having a universallymounted rotor decoupled from a vertically oriented driving shaft,pickoff and torquer means formed on the gyroscope and interconnected totorque-balance the rotor when the shaft is moved in response to theeaRth''s rotation and means energized by said pickoffs and torquers forresolving signals therefrom into an indication of the position of truenorth.
 16. A north-seeking gyroscope as recited in claim 15 wherein saidrotor is connected to said drive shaft by a transverse planar memberhaving portions connected to the rotor and the shaft which areuniversally connected through an intermediate, inertia portion on twoperpendicular axes and means for preventing axial movement of the rotorwith respect to the shaft, said gyroscope additionally comprising meansfor driving the rotor at a speed at which the inertia and springconstants of the universal joint are canceled.
 17. A gyroscope asrecited in claim 16 additionally comprising solenoid means including anaxially extending coil concentrically disposed with respect to the shaftaxis adapted to be energized by a direct current source, an annular,radially polarized magnet, and a pair of radially spaced, annular poleshoes axially extending from the radial terminations of said magnets tobe partially axially coextensive with said coil when the rotor spin axisand the shaft axis are aligned whereby energization of the coil producesa torque about the gyroscope axes which compensates for torques producedwhen said rotor is displaced.